scholarly journals Experimental Study of the Thermal Behavior of a Watercress Planted Roofed Cubic Cell to be Watered with Domestic Wastewater

2021 ◽  
pp. 19-30
Author(s):  
Dominique Morau ◽  
Ives Abel Fetra Andriatsitohaina Rabesah ◽  
Hery Tiana Rakotondramiarana
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Ambient Temperature ◽  
Energy Savings ◽  
Domestic Wastewater ◽  
Energy Performance ◽  
Conventional Concrete ◽  
Apparent Thermal Conductivity ◽  
Fluctuation Amplitude

One of the virtues of watercress is its ability to grow in wastewater. This work aims at experimentally studying the thermal behavior of a watercress planted roofed cubic cell. To do this, the temperatures of various components of the cell and the solar radiation received by this cell were measured in order to compare the watercress roof performance with that of the conventional concrete roof. Then, the influence of the opening applied on the door of the studied cell was analyzed. As results, the fluctuation amplitude of the indoor ambient temperature of the concrete roofed cell is wider than that of the green roofed cell. Moreover, the last opening applied to the facades of the cell was the optimum area that the ambient temperature indoor was more attenuated. The LAI’s crop was worth 1.2. In addition, the low value of the canopy apparent thermal conductivity revealed that this layer plays a role of thermal insulation. The rooftop greening allows energy savings of about 85% compared to the consumed energy with conventional roofing. An extension of this work could be the energy performance analysis of a system using renewable energy for pumping domestic wastewater produced in or around green roofed housing.

scholarly journals Analytical Model for the Channel Maximum Temperature in Ga2O3 MOSFETs

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Xiaole Jia ◽  
Haodong Hu ◽  
Genquan Han ◽  
Yan Liu ◽  
Yue Hao
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Ambient Temperature ◽  
Numerical Simulations ◽  
Thermal Management ◽  
Power Density ◽  
Analytical Model ◽  
Maximum Temperature ◽  
Comsol Multiphysics ◽  
Increasing Temperature

AbstractIn this work, we proposed an accurate analytical model for the estimation of the channel maximum temperature of Ga2O3 MOSFETs with native or high-thermal-conductivity substrates. The thermal conductivity of Ga2O3 is anisotropic and decreases significantly with increasing temperature, which both are important for the thermal behavior of Ga2O3 MOSFETs and thus considered in the model. Numerical simulations are performed via COMSOL Multiphysics to investigate the dependence of channel maximum temperature on power density by varying device geometric parameters and ambient temperature, which shows good agreements with analytical model, providing the validity of this model. The new model is instructive in effective thermal management of Ga2O3 MOSFETs.

Role of Interface Thermal Boundary Resistance, Straining, and Morphology in Thermal Conductivity of a Set of Si-Ge Superlattices and Biomimetic Si-Ge Nanocomposites

2011 ◽  
Author(s):  
Vikas Samvedi ◽  
Vikas Tomar
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Boundary Resistance ◽  
Thermal Boundary Resistance ◽  
Structural Factors ◽  
Transfer Resistance ◽  
Different Temperatures ◽  
Non Equilibrium Molecular Dynamics ◽  
Striking Contrast

Nanoscale engineered materials with tailored thermal properties are desirable for applications such as highly efficient thermoelectric, microelectronic and optoelectronic devices. It has been shown earlier that by judiciously varying interface thermal boundary resistance (TBR) thermal conductivity in nanostructures could be controlled. Two types of nanostructures that have gained significant attention owing to the presence of TBR are superlattices and nanocomposites. A systematic comparison of thermal behavior of superlattices and nanocomposites considering their characteristic structural factors such as periodicity and period length for superlattices, and morphology for nanocomposites, under different extents of straining at a range of temperatures remains to be performed. In this presented work, such analyses are performed for a set of Si-Ge superlattices and Si-Ge biomimetic nanocomposites using non-equilibrium molecular dynamics (NEMD) simulations at three different temperatures (400 K, 600 K, and 800 K) and at strain levels varying between −10% and 10%. The analysis of interface TBR contradicts the usual notion that each interface contributes equally to the heat transfer resistance in a layered structure. The dependence of thermal conductivity of superlattice on the direction of heat flow gives it a characteristic somewhat similar to a thermal diode as found in this study. The comparison of thermal behavior of superlattices and nanocomposites indicate that the nanoscale morphology differences between the superlattices and the nanocomposites lead to a striking contrast in the phonon spectral density, interfacial thermal boundary resistance, and thermal conductivity. Both compressive and tensile strains are observed to be important factors in tailoring the thermal conductivity of the analyzed superlattices, whereas have very insignificant influence on the thermal conductivity of the analyzed nanocomposites.

scholarly journals Modeling of a PCM TES Tank Used as an Alternative Heat Sink for a Water Chiller. Analysis of Performance and Energy Savings

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3652 ◽  
Author(s):  
Real-Fernández ◽  
Navarro-Esbrí ◽  
Mota-Babiloni ◽  
Barragán-Cervera ◽  
Domenech ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Heat Sink ◽  
Phase Change Materials ◽  
Energy Savings ◽  
Energy Performance ◽  
Coefficient Of Performance ◽  
Maximum Deviation ◽  
Outlet Temperature ◽  
Vapor Compression ◽  
Transient Model

Phase change materials (PCMs) can be used in refrigeration systems to redistribute the thermal load. The main advantages of the overall system are a more stable energy performance, energy savings, and the use of the off-peak electric tariff. This paper proposes, models, tests, and analyzes an experimental water vapor compression chiller connected to a PCM thermal energy storage (TES) tank that acts as an alternative heat sink. First, the transient model of the chiller-PCM system is proposed and validated through experimental data directly measured from a test bench where the PCM TES tank is connected to a vapor compression-based chiller. A maximum deviation of 1.2 °C has been obtained between the numerical and experimental values of the PCM tank water outlet temperature. Then, the validated chiller-PCM system model is used to quantify (using the coefficient of performance, COP) and to analyze its energy performance and its dependence on the ambient temperature. Moreover, electrical energy saving curves are calculated for different ambient temperature profiles, reaching values between 5% and 15% taking the experimental system without PCM as a baseline. Finally, the COP of the chiller-PCM system is calculated for different temperatures and use scenarios, and it is compared with the COP of a conventional aerothermal chiller to determine the switch ambient temperature values for which the former provides energy savings over the latter.

Role of Interface Thermal Boundary Resistance, Straining and Morphology in Thermal Conductivity of a Set of Si-Ge Superlattices and Biomimetic Si-Ge Nanocomposites

2011 ◽  
Author(s):  
Vikas Samvedi ◽  
Vikas Tomar
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Boundary Resistance ◽  
Thermal Boundary Resistance ◽  
Structural Factors ◽  
Transfer Resistance ◽  
Different Temperatures ◽  
Non Equilibrium Molecular Dynamics ◽  
Striking Contrast

Nanoscale engineered materials with tailored thermal properties are desirable for applications such as highly efficient thermoelectric, microelectronic and optoelectronic devices. It has been shown earlier that by judiciously varying interface thermal boundary resistance (TBR) thermal conductivity in nanostructures could be controlled. Two types of nanostructures that have gained significant attention owing to the presence of TBR are superlattices and nanocomposites. A systematic comparison of thermal behavior of superlattices and nanocomposites considering their characteristic structural factors such as periodicity and period length for superlattices, and morphology for nanocomposites, under different extents of straining at a range of temperatures remains to be performed. In this presented work, such analyses are performed for a set of Si-Ge superlattices and Si-Ge biomimetic nanocomposites using non-equilibrium molecular dynamics (NEMD) simulations at three different temperatures (400 K, 600 K, and 800 K) and at strain levels varying between −10% and 10%. The analysis of interface TBR contradicts the usual notion that each interface contributes equally to the heat transfer resistance in a layered structure. The dependence of thermal conductivity of superlattice on the direction of heat flow gives it a characteristic somewhat similar to a thermal diode as found in this study. The comparison of thermal behavior of superlattices and nanocomposites indicate that the nanoscale morphology differences between the superlattices and the nanocomposites lead to a striking contrast in the phonon spectral density, interfacial thermal boundary resistance, and thermal conductivity. Both compressive and tensile strains are observed to be important factors in tailoring the thermal conductivity of the analyzed superlattices, whereas have very insignificant influence on the thermal conductivity of the analyzed nanocomposites.

The methodology of experimental research of the feed components extrusion process in order to improve its energy performance

2020 ◽  
pp. 147-152
Author(s):  
E. M. Ratnikov ◽  
D. O. Milko
Keyword(s):  
Experimental Studies ◽  
Energy Performance ◽  
Extrusion Process ◽  
Mathematical Methods ◽  
Screw Extruder ◽  
Mathematical Planning ◽  
Factors Affecting ◽  
Extrusion Processing ◽  
Definition Of

Annotation Purpose. Development of a program and methods for conducting experimental studies of the extrusion process with the definition of parameters and modes of operation of the extruder to improve its energy performance. Methods. Methods of mathematical statistics, synthesis, analysis, description and modeling were used. Results. The application of mathematical methods, in particular mathematical planning, reduces the number of experiments several times, and allows to evaluate the role of influencing factors, obtain a mathematical model of the process and determine the optimal conditions for its parameters and modes, etc. Conclusions. The methodology for experimental studies of a screw extruder is presented with the necessary equipment and methodology for processing the obtained experimental data. A mathematical method of planning, which reduces the number of experiments several times, allows us to evaluate the role of factors affecting productivity and energy intensity is presented. Keywords: extruder, auger, nutrients, research methodology, extrusion, processing, feed.

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

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